Eufemiano Fuentes has again refused to reveal details of football clubs he has worked with, saying threats had been made against him and his family in the past.
Fuentes, the controversial Spanish doctor awaiting the verdict in the Operacion Puerto trial for alleged doping-related offences in cycling, told Marca on Friday that he knew who had made threats against him in 2006 and continued to take them very seriously.
"I know who [the people were who made the threats], but I am not going to say that here. They were threats against me and my family," he said.
A Le Monde story in 2006 claimed Fuentes had worked with La Liga clubs including Real Madrid and Barcelona. Both clubs subsequently took legal action and were awarded damages when the allegation was withdrawn.
In March, Fuentes claimed he was still owed money by Real. The club released a statement clarifying that the alleged debt related to his appearance as a witness as a trial over the Le Monde allegations, and he subsequently said he had never treated any Real players.
The Puerto proceedings also led to a claim from Real Sociedad president Inaki Badiola that Fuentes had worked for that club in the past - a claim former president Jose Luis Astiazaran strenuously denied.
Asked by Marca if a label saying RSOC which appeared as evidence in court referred to the Basque club, Fuentes said it was strange the current investigation had not looked further into deciphering the code.
"I am not going to answer that question," he said. "I do not confirm or deny it. [But] yes, it is at the very least surprising [that this route was not further investigated]."
Fuentes said the code 'Milan' in his files was not an indicator of Serie A club AC Milan. "That does not refer to the team Milan, but it could have a relation to football," he said.
The doctor, employed by Las Palmas when the Canary Islands club gained promotion to the Spanish top flight in 2000-01, denied he had treated any "player of the Spanish national team", but said he had also worked for other big La Liga clubs and treated players, without naming them.
"When you say 'big clubs' who do you mean?" he said. "Madrid and Barcelona? No. But if big clubs are those who play in the Primera Division, the answer would be different."
The three-month long court case has heard evidence from many cyclists, including Tyler Hamilton and Jorg Jaksche, but has not investigated evidence of doping in other sports.
Fuentes has spoken publicly of having treated footballers, basketball players, athletes, tennis players and boxers, and has suggested cycling is being victimised by the authorities.
He and his four co-accused have not been charged with doping, which was not illegal in Spain at the time under consideration. However, all could face prison if Judge Julia Patricia Santamaria finds they carried out medical procedures in an unsafe environment.
Fuentes and his co-accused maintain that they did nothing illegal.